In an information record/reproduction apparatus provided in an artificial satellite, it is customary to divide all storage area into areas each having a physically fixed size and to record information of the same priority into each of the areas. Therefore, even if information is of a high priority, it cannot be recorded with a size greater than the size of an area into which the information is to be recorded. On the other hand, if information of a low priority has a size less than initially expected, a free space is present in an area into which the information is to be recorded. However, such a free storage area cannot be used effectively.
Additionally, there is another problem that, even if information of a high priority has a size that is greater than initially expected and exceeds the size of an area into which the information is to be recorded, such information of a high priority cannot newly be recorded into an area that has stored information of a low priority that does not need to be reproduced.
Specific examples will be described below.
An information record/reproduction apparatus in an artificial satellite is used to reproduce information from the information record/reproduction apparatus in the order of the priority and to transmit the information in its intended order of the priority.
FIG. 4 illustrates an example of a recording scheme of a volume group 10 in an existing information record/reproduction apparatus provided in a scientific satellite. With this recording scheme, all storage areas are managed as a physical medium of a physical volume 40 by a memory manager 20. Physical extents 50 (#00, #01, . . . , #XX) are allocated as fixed-size storage areas to respective categories of information to be recorded. Specifically, each of the physical extents 50 (#00, #01, . . . , #XX) includes one or more blocks 60. The number of the blocks is predetermined.